Systems and methods for improving flow in radial flow reactor

ABSTRACT

A scallop, center pipe, and outer basket for use in a radial flow reactor are provided. Each of the scallop, the center pipe, and the outer basket is formed of an elongated conduit having a top end and an opposing bottom end, and a plurality of openings formed in the elongated conduit through a thickness thereof. A diameter of the plurality of openings progressively increases or decreases from the top end to the opposing bottom end of the elongated conduit so as to allow a feedstock to flow radially out through the plurality of openings on the scallop or outer basket, or to allow a feedstock to flow uniformly into the center pipe through the plurality of openings. A system utilizing the center pipe together with either the scallop or the outer basket is also provided.

FIELD OF THE INVENTION

The invention relates to various systems and methods of improving theflow of gas, vapors, or liquids through a radial flow reactor tooptimize the catalyst reaction and catalyst life.

BACKGROUND OF THE INVENTION

In refining chemical and petrochemical applications, conventionalscallops are used in radial flow reactors and function as conduitsthrough which gases, vapors or liquids (hereinafter referred tocollectively as “G-V-L” or “feedstock”) flow inside the reactor vessel.Scallops are typically formed as elongated, tube-shaped conduits ofvarious geometry, typically having a cross-sectional “D” shape (althoughother shapes are also used), through which G-V-L flow radially in aninward or outward direction relative to the vessel. The scallops aretypically formed of various metal constructions, sometimes havingopenings on a surface thereof to allow the G-V-L to flow freely throughthe surface of the scallop, as well as along the length of the scallop.When the G-V-L flows through the scallop and escape through the openingson the surface, it comes into contact with catalyst particles containedwithin an adjacent catalyst bed (annulus space), thus causing a reactionto take place. In use, the scallops are placed adjacent to one anotheralong the inner circumference of the wall of the reactor vessel.Scallops in the art have generally used holes of uniform size anddistribution over the body of the scallop.

In refining chemical and petrochemical applications in radial flowreactors, conventional outer baskets may also be used in place of, or inaddition to, the scallops discussed above. These outer baskets providethe same function as the scallops, i.e., as conduits through which G-V-Lflow inside the reactor vessel. Outer baskets are typically formed asone continuous basket, such as a cylindrical-shaped conduit of variousgeometry, through which G-V-L flow radially in an inward or outwarddirection relative to the vessel. The outer basket is typically formedof various metal constructions, sometimes having openings on a surfacethereof to allow the G-V-L to flow freely through the surface of theouter basket, as well as along the length of the outer basket. When theG-V-L flows through the outer basket and escapes through the openings onthe surface, it comes into contact with catalyst particles containedwithin an adjacent catalyst bed (annulus space), thus causing a reactionto take place. In use, the outer basket is placed along the innercircumference of the wall of the reactor vessel. Outer baskets in theart have generally used profile wire with various wire slot openings ofuniform size and distribution over the body of the outer basket.

Likewise, conventional center pipes are also used in radial flowreactors and function as conduits through which G-V-L flow inside thereactor vessel. Center pipes are typically formed as one continuouscylinder, through which G-V-L flow radially in an inward or outwarddirection relative to the vessel. The center pipe is typically formed ofvarious metal constructions, sometimes having openings on a surfacethereof to allow the G-V-L to flow freely through the surface of thecenter pipe, as well as along the length of the center pipe. When theG-V-L flows through the adjacent catalyst bed, the center pipe acts asthe collection/outlet device after the reaction has taken place. In use,the center pipes are placed directly in the center of the reactor tocreate a uniform annulus for the catalyst bed of the reactor vessel.Center pipes in the art generally have holes of uniform size anddistribution over the surface of the center pipe to hydraulicallycontrol the adjacent catalyst bed. The center pipe is then generallywrapped with a wire mesh or profile wire material for the purpose ofcatalyst containment.

One common problem with such designs is that as the G-V-L enters thescallop or outer basket, a higher volume of the G-V-L outflows throughthe openings of the scallop or outer basket where the pressure drop ofthe system is lower. This difference in flow could be seen in both theaxial and radial directions. This uneven flow distribution through andalong the scallop or outer basket, results in an uneven utilization ofthe catalyst in the catalyst bed. Specifically, the top part of thecatalyst bed is prone to be utilized more quickly, while the bottom partof the catalyst bed is slow to be utilized. This can cause a number ofproblems, most significantly (and costly) that the uneven flowdistribution reduces the resulting reaction efficiency of the vessel.

Accordingly, systems and methods of improving the flow distribution ofG-V-L through the reactor vessel are needed, in order to increasereaction efficiency, catalyst activity, and catalyst bed uniformity, soas to extend the lifespan of the catalyst, and to increase reactorequipment efficiencies and ancillary equipment performance. Morespecifically, a system that causes a more uniform pressure drop andtherefore G-V-L flow in the reactor system is desired.

SUMMARY OF THE INVENTION

To solve this problem, the invention provides modified scallops, centerpipes, and outer baskets for use in a radial flow reactor whichmanipulate the flow of G-V-L through the reactor vessel to optimize thecatalyst reaction.

The invention is directed to a scallop for use in a radial flow reactorwhich includes an elongated conduit having a top end and an opposingbottom end, and a plurality of openings formed in the elongated conduitthrough a thickness thereof. A diameter of the plurality of openingsprogressively increases or decreases from the top end to the opposingbottom end of the elongated conduit so as to allow a feedstock to flowuniformly out of the scallop through the plurality of openings.

The invention also provides a scallop for use in a radial flow reactorwhich includes an elongated conduit having a top end, an opposing bottomend, and opposing sides, and a plurality of openings formed in theelongated conduit through a thickness thereof. A diameter of theplurality of openings progressively increases or decreases from acenterline of the elongated conduit to each of the opposing sides, so asto allow a feedstock to flow uniformly out of the scallop through theplurality of openings.

The invention is also directed to a center pipe for use in a radial flowreactor which includes an elongated conduit having a top end and anopposing bottom end, and a plurality of openings formed in the elongatedconduit through a thickness thereof. A diameter of the plurality ofopenings progressively increases or decreases from the top end to theopposing bottom end of the elongated conduit so as to allow a feedstockto flow uniformly into the center pipe through the plurality ofopenings.

The invention further provides an outer basket for use in a radial flowreactor which includes an elongated conduit having a top end and anopposing bottom end, and a plurality of openings formed in the elongatedconduit through a thickness thereof. A diameter of the plurality ofopenings progressively increases or decreases from the top end to theopposing bottom end of the elongated conduit so as to allow a feedstockto flow uniformly out of the outer basket through the plurality ofopenings.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete appreciation of the invention and many of the attendantadvantages thereof will be readily obtained as the same becomes betterunderstood by reference to the following detailed description whenconsidered in connection with the accompanying drawings, wherein:

FIG. 1A is a cross-sectional top view of a radial flow reactor vesselutilizing scallops in accordance with an embodiment of the invention;

FIG. 1B is a cross-sectional top view of a radial flow reactor vesselutilizing an outer basket in accordance with an embodiment of theinvention;

FIG. 2A is a perspective view of a scallop for use in a reactor vesselin accordance with an embodiment of the invention, representing anopening gradient of small to large, from top to bottom, respectively;

FIG. 2B is an enlarged view of the scallop illustrated in FIG. 2A takenalong line A;

FIG. 2C is an enlarged front view of the scallop illustrated in FIG. 2Aalong the scallop centerline;

FIG. 2D is a perspective view of a scallop for use in a reactor vesselin accordance with an embodiment of the invention, representing anopening gradient of large to small from top to bottom, respectively;

FIG. 2E is a perspective view of a profile wire scallop overlay for usewith a scallop according to an embodiment of the invention;

FIG. 2F is an enlarged view of the profile wire scallop overlayillustrated in FIG. 2E taken along line B;

FIG. 2G is a front perspective view of the scallop of FIG. 2A or FIG. 2Dcoupled to the profile wire scallop overlay of FIG. 2E, creating ascallop assembly according to an embodiment of the invention;

FIG. 3A is a perspective view of a center pipe according to anembodiment of the invention representing an opening gradient of small tolarge, from top to bottom, respectively;

FIG. 3B is an enlarged view of the center pipe illustrated in FIG. 3Ataken along line C;

FIG. 3C is a perspective view of a center pipe according to anembodiment of the invention representing an opening gradient or large tosmall, from top to bottom, respectively;

FIG. 3D is an enlarged view of the center pipe illustrated in FIG. 3Ctaken along line D;

FIG. 3E is a perspective view of a profile wire center pipe overlay foruse with a center pipe according to an embodiment of the invention;

FIG. 3F is an enlarged view of the profile wire center pipe overlayillustrated in FIG. 3E, taken along line E;

FIG. 3G is a perspective view of the profile wire center pipe overlay ofFIG. 3E installed with the center pipe of FIG. 3A or FIG. 3C accordingto an embodiment of the invention;

FIG. 4A is a perspective view of an outer basket according to anembodiment of the invention representing an opening gradient of small tolarge, from top to bottom, respectively;

FIG. 4B is an enlarged view of the outer basket of FIG. 4A, taken alongline F;

FIG. 4C is a perspective view of an outer basket according to anembodiment of the invention representing an opening gradient of large tosmall, from top to bottom, respectively;

FIG. 4D is an enlarged view of the outer basket of FIG. 4C, taken alongline G;

FIG. 4E is a perspective view of a profile wire outer basket overlay foruse with an outer basket according to an embodiment of the invention;

FIG. 4F is an enlarged view of the profile wire outer basket overlayillustrated in FIG. 4E, taken along line H; and

FIG. 4G is a perspective view of the profile wire outer basket overlayof FIG. 4D installed inside of the outer basket of FIG. 4A or FIG. 4Caccording to an embodiment of the invention.

DETAILED DESCRIPTION

The invention provides systems and methods of improving flowdistribution of gases, vapors, and liquids (hereinafter collectivelyreferred to as “G-V-L” or “feedstock”) through the reactor vessel toreduce or eliminate known problems associated with uneven flow. Thesystems and methods set forth herein: (1) reduce the occurrence ofcoking which can cause downstream catalyst restriction (pluggingtransfer lines), and which in turn reduces the catalyst surfacetemperature during regeneration, thus increasing catalyst and equipmentlife, (2) reduce the occurrence of hot and cold spots within the reactorvessel, particularly on the reactor walls, which in turn increases thelifespan of the catalyst and reactor vessel equipment, and reducespotential damage to CP due to hot spots, (3) increase cycle length, (4)increase yield by minimizing high residence-time areas, (5) decrease thepressure drop of G-V-L across the catalyst bed, (6) decrease foulingpotential, (7) decrease potential for catalyst pinning, and (8) increasethe reliability of the equipment which decreases the potential for lossof containment and migration of the catalyst to downstream equipment.

As set forth herein, the invention provides improvements to componentsof the reactor vessel which are designed to reduce or eliminate theproblems associated with uneven flow distribution. In one aspect of theinvention, modified scallops are provided. In another aspect of theinvention, modified center pipes are provided. In another aspect of theinvention, modified outer baskets are provided. The modified scallopsmay be used together with conventional center pipes known in the art, orthey may be used with the modified center pipes disclosed herein. Themodified outer basket may be used together with conventional centerpipes known in the art, or they may be used with the modified centerpipes disclosed herein. Likewise, the modified center pipes may be usedtogether with conventional scallops known in the art, or they may beused with the modified scallops disclosed herein. Likewise, the modifiedcenter pipes may be used together with conventional outer baskets knownin the art, or they may be used with the modified outer basketsdisclosed herein.

Radial Flow Reactor

A cross-sectional view of the inside of a reactor vessel 100 isillustrated in FIG. 1A. In this embodiment, scallops 104 are used. Theoutermost surface of the reactor vessel 100 is an outer shell 102.Within the reactor vessel 100, a plurality of scallops 104 are arrangedcircumferentially around an inner wall 106 of the vessel 100. Asillustrated, the back surface 108 of the scallops 104 are positioneddirectly adjacent to the inner wall 106, while the distribution surface110 of the scallops 104 is exposed to the interior of the vessel 100.The scallops 104 are preferably held in place along the inner wall 106of the vessel 100 by expander rings (not shown), although any knownmethod of securing scallops within a reactor vessel may be used.

A cross-sectional view of an alternative reactor vessel 120 isillustrated in FIG. 1B. In this embodiment, an outer basket 116 is usedinstead of a plurality of scallops. The outer basket 116 is arrangedcircumferentially around the inner wall 106 of the vessel 120. Asillustrated, the outer surface 118 of the outer basket 116 is positioneddirectly adjacent to the inner wall 106, while the distribution surface122 of the outer basket 116 is exposed to the interior of the vessel120. In this embodiment, a profile wire overlay 124, discussed morefully below, is installed inside of the outer basket 116. The outerbasket 116 is preferably held in place along the inner wall 106 of thevessel 100 by cover deck assemblies or other mechanical solutions knownin the art (not shown); any known method of securing outer basket withina reactor vessel may be used.

In either embodiment illustrated in FIG. 1A or 1B, directly adjacent tothe distribution surface 110 of each of the scallops 104, or the outerbasket 116, is at least one catalyst bed 112. The catalyst bed(s) 112contains a catalyst. The reactor catalyst bed(s) 112 may be arrangedindividually in a side by side design or in a stacked design. Typically,the reactors are arranged in series, typically 3-4 catalyst beds 112,however they can also be arranged in parallel. In either arrangement,the catalyst beds 112 are either radial fixed beds or moving beds(fluidized or not fluidized).

At the center of the reactor vessel 100 or 120 is the center pipe 114.When the feedstock gas, such as naphtha, ammonia, or other G-V-L, flowsdown into the scallops 104 or the outer basket 116 and escapes throughthe openings therein, it comes into contact with the catalyst bed(s)112, thus causing a reaction to take place. The feedstock G-V-L thenflows into the center pipe 114 and out of the reactor vessel 100 orreactor vessel 120. The movement of the feedstock G-V-L into and out ofthe vessel 100 or vessel 120 at different rates can cause variances inpressure within the vessel 100 or vessel 120. In use, the feedstockshould flow through the scallops 104 or the outer basket 116 into thecatalyst bed 112 and then through the center pipe 114. In certainembodiments, the flow pattern of the feedstock may be opposite, but suchflow patterns are not discussed in detail herein.

As set forth herein, modified scallops, modified outer baskets, and/ormodified center pipes may each be utilized in a reactor vessel, such asthose illustrated in FIGS. 1A and 1B. These components may be usedtogether, or they may be used with other conventional reactor vesselcomponents. Each of the modified components is discussed in detailbelow.

Modified Scallops

One aspect of the invention relates to a “modified” scallop (hereinafterreferred to as a “scallop”) for use in radial flow reactor vessels whichimproves G-V-L flow distribution through the reactor. A scallopaccording to various embodiments of the invention is illustrated inFIGS. 2A-G. The scallop utilizes openings having a modified size and/orshape along its length and width in order to adjust the flowdistribution of the G-V-L through the reactor vessel. Generally, smalleropenings are used where the G-V-L enters the scallop and scales tolarger openings further from the G-V-L entry point in the verticalplane. This pattern can also be designed with larger openings where theG-V-L enters the scallop and scales to smaller openings further from theG-V-L entry point in the vertical plane. Generally, smaller openings areused where the scallop surface protrudes deepest into the adjacentcatalyst bed and gradually increase to a larger gradient as the scallopnears the inside diameter of the reactor vessel creating a uniform G-V-Lentry point in the horizontal plane, regardless of the vertical holearrangement. The design is to create reasonably equivalent pressure dropacross all openings along the length and along the width of the scallopbody.

Scallops may be constructed of various geometries of an elongatedconduit, typically having a “D”-shaped cross-section, which is where thename “scallops” originates. However, scallops may also have differentcross sectional shapes, such as triangular or trapezoidal. They aretypically formed of various metal construction which is manufacturedinto their desired shape. Suitable scallop designs are presented in U.S.Pat. Nos. 5,209,908, 5,366,704 and 6,224,838, and are incorporatedherein by reference.

As illustrated in FIG. 2A, the scallop 200 has an inner surface 202 andan outer surface 204. The scallop 200 includes a plurality of openings208 (see FIG. 2C) along its length and width that extend through theentire thickness of the scallop, from the inner surface 202 to the outersurface 204. The openings 208 allow the G-V-L flowing inside of thescallop 200 to outflow through the scallop, thus coming into contactwith the catalyst bed contained in the reactor vessel. Specifically,when the G-V-L outflow through the openings 208 on the scallop 200, theycome into contact with catalyst particles contained within an adjacentcatalyst bed, thus causing a reaction to take place.

In the prior art, the openings in the scallop are generally of the samesize and shape along the entire length of the scallop. These scallopshave a tendency to cause a higher volume of G-V-L to outflow through theopenings toward the top of the scallop, since the higher inflow pressureacross the same size opening causes more G-V-L to flow, while a lesservolume of the G-V-L outflows through the openings toward the bottom ofthe scallop where pressure is lower. This creates an uneven G-V-L flowdistribution through the scallop, thereby causing an uneven utilizationof the catalyst.

As illustrated in FIG. 2A, however, the openings 208 toward the top end210 of the scallop 200 have a smaller diameter than the openings 208toward the bottom end 212 of the scallop 200. By way of a non-limitingexample, the openings 208 toward the top end 210 of the scallop 200 mayhave a diameter of about 1 mm, while the openings 208 toward the bottomend 212 of the scallop 200 may have a diameter of about 75 mm. In thisway, when the G-V-L enters the scallop 200, a lower volume outflowsthrough the smaller openings 208 at the top end 210 of the scallop 200,while a relatively higher volume outflows through the larger openings208 at the bottom end 212 of the scallop 200, since the larger openingsconstitute the path of least resistance. Thus, the scallop 200 can beused to manipulate the distribution of flow of G-V-L through the reactorvessel to optimize the catalyst reaction. An enlarged view of theopenings 208, taken along line A of FIG. 2A, is illustrated in FIG. 2B.

In another embodiment illustrated in FIG. 2D, the openings 208 towardthe top end 210 of the scallop 200 have a larger diameter than theopenings 208 toward the bottom end 212 of the scallop 200′. By way of anon-limiting example, the openings 208 toward the bottom end 212 of thescallop 200′ may have a diameter of about 1 mm, while the openings 208toward the top end 210 of the scallop 200′ may have a diameter of about75 mm. In this way, when the G-V-L enters the scallop 200′, a highervolume outflows through the larger openings 208 at the top end 210 ofthe scallop 200′, while a relatively smaller volume outflows through thesmaller openings 208 at the bottom end 212 of the scallop 200′, sincethe larger openings constitute the path of least resistance. Thus, thescallop 200′ can be used to manipulate the distribution of flow of G-V-Lthrough the reactor vessel to optimize the catalyst reaction.

In yet another embodiment, the openings 208 may have a horizontalgradient pattern, as illustrated in FIG. 2C. Specifically, the openings208 may have varying sizes along the width of the scallop 200, insteadof along the length of the scallop 200 as is shown in FIGS. 2A and 2D.For example, the scallop 200 may have its largest openings on the sides214 of the scallops, and smaller openings 208 closer to the center ofthe scallop 200, along the center line 216. In another embodiment, theopenings 208 may be largest at the center line 216 of the scallop 200and smallest at the sides 214 of the scallop 200. In this way, a moreuniform volume of G-V-L will flow out of the sides and the front of thescallop 200, thus directing the G-V-L outflow more efficiently towardthe catalyst bed.

In yet another embodiment, the openings 208 may increase and thendecrease, or decrease and then increase, along the length of the scallop200, or along the width of the scallop 200, such that there is anon-uniform change in the opening size from the top end 210 to thebottom end 212 and/or from the center line 216 to the sides 214 of thescallop.

In another embodiment, the spacing of the openings 208 may be modifiedto adjust the G-V-L flow distribution (not shown). In this embodiment,each of the openings 208 at and adjacent to the top end 210 of thescallop 200 may be spaced closer together, and have relatively largeropening size, to provide a larger total surface area of openings 208 toincrease G-V-L outflow. On the other hand, at the bottom end 212 of thescallop 200, the openings 208 may be spaced farther apart, together witha relatively smaller opening size, so that the total surface area ofopenings 208 is lower at the bottom end 212 than at the top end 210 ofthe scallop 200. For example, the openings 208 at either the top end 210or the bottom end 212 may be arranged such that each opening 208 isspaced about 0.5 mm-25 mm apart from an adjacent opening 208.Alternatively, the openings 208 at and adjacent to the top end 210 maybe spaced farther apart, together with a relatively smaller openingsize, so that the total surface area of the openings 208 is lower at thetop end 210, as compared to the bottom end 212.

The same is true where the scallop 200 has a horizontal, as opposed tovertical, gradient pattern. In this embodiment, the openings 208 at thecenter line of the scallop 200 may be spaced farther apart from theopenings 208 at the sides of the scallop 200, or vice versa.

The openings 208 on the scallop 200 are generally circular in shape,although any shape, such as square, rectangular, triangular, oval,oblong, or any other shape suitable for use in a particular application,may be used. In a preferred embodiments, the openings 208 are round inshape.

As illustrated in FIG. 2E-2G, the scallop 200 may be used together withprofile wire scallop overlay 218, although it is not required accordingto the invention. The profile wire overlay 218 preferably has the sameor similar shape as the scallop 200 and is configured to be placed overand coupled to the distribution surface of the scallop 200. The profilewire scallop overlay 218 may be coupled to the scallop 200 according toany known means, such as, for example, welding. A scallop 200 coupled toa profile wire scallop overlay 218 is illustrated in FIG. 2G, forming acomplete scallop assembly.

As shown in FIG. 2F, the profile wire scallop overlay 218 preferablyincludes a plurality of slots 220 along its length, which may beconfigured vertically or horizontally depending upon the particularapplication. As shown in the enlarged view of FIG. 2F, taken along lineB of FIG. 2E, the slots 220 are arranged vertically with respect to theelongated length of the profile wire scallop overlay 218. The profilewire scallop overlay 218 prevents catalyst particles from the adjacentcatalyst bed from flowing into the scallops 200, while still allowingG-V-L to outflow from the scallops 200. The size, shape, and placementof the slots 220 on the profile wire scallop overlay 218 may also bemodified, but such modifications will typically not dictate G-V-L flowpattern through the scallops 200. However, designs could be used toimpact flow through the profile wire scallop overlay 218.

It should be noted that the scallop 200 and the profile wire scallopoverlay 218 may have any size suitable for use in a particularapplication in a specific type of reactor vessel. In one embodiment,they may be about 1-25 meters long and have an overall width of about 10cm-1 m, with the largest opening of the conduit being 10 cm-1 m (withreference to FIGS. 1A-1B, measured from the back surface 108 to thedistribution face surface 110 of the scallop 104). Their size is notparticularly limited, as it dictates the volume of G-V-L that can bepassed through depending on the particular application.

The scallop 200 and the profile wire scallop overlay 218 may be formedof any material known to one skilled in the art, including, but notlimited to, metals, ceramics, polymers, composites, and the like. In apreferred embodiment, they are formed of metal, preferably a metallicalloy, which is strong enough to withstand the elevated temperatures,pressures, catalyst movement and G-V-L flow rates inside the reactorvessel without deforming. For example, they may be formed of stainlesssteel. The material used to form the scallop 200 and/or the profile wirescallop overlay 218 is not particularly limited, as long as it hassufficient strength to withstand the operating conditions of thereactor. In one embodiment, although not required, the scallop 200and/or the profile wire scallop overlay 218 may be provided with acoating or surface treatment, such as an anti-corrosion coating.

Modified Center Pipes

Another aspect of the invention relates to a “modified” center pipe(hereinafter referred to as a “center pipe”) for use in radial flowreactor vessels which improves G-V-L flow distribution through thereactor. Center pipes according to various embodiments of the inventionare illustrated in FIGS. 3A-D. The center pipe utilizes openings havinga modified size and/or shape along its length in order to adjust theflow distribution of the G-V-L through the reactor vessel. Generally,smaller openings are used where the feedstock G-V-L enters the centerpipe and scales to larger openings further from the G-V-L entry point,but the center pipe may also be designed with larger openings being usedwhere the feedstock G-V-L enter the center pipe and scales to smalleropenings further form the G-V-L entry point. The design is to createreasonably equivalent pressure drop across all openings up and down thecenter pipe.

Center pipes may be constructed of various geometries of an elongatedconduit or cylinder. However, center pipes may also have different crosssectional shapes, such as triangular or trapezoidal. They are typicallyformed of various metal construction which is manufactured into theirdesired shape.

As shown in FIG. 3A, the center pipe 300 is an elongated conduit, suchas a tube-shaped member, that has an inner surface 302 and an outersurface 304. In one embodiment, the center pipe 300 includes a pluralityof openings 308 along its length that extend through the entirethickness of the center pipe 300, from the inner surface 302 to theouter surface 304. The openings 308 allow the G-V-L that have reactedwith the catalyst bed 112 to flow into the interior of the center pipe300 and out of the reactor vessel.

In prior art structures, center pipe openings are generally of the samesize and shape along the entire length of the center pipe. Asillustrated in FIG. 3A, however, the openings 308 toward the top end 310of the center pipe 300 have a smaller diameter than the openings 308toward the bottom end 312 of the center pipe 300. By way of anon-limiting example, the openings 308 toward the top end 310 of thecenter pipe 300 may have a diameter of about 0.1 mm, while the openings308 toward the bottom end 312 of the center pipe 300 may have a diameterof about 75 mm. In this way, after the G-V-L reacts with the catalystbed, a lower volume flows into the center pipe 300 at the top end 310 ofthe center pipe 300, while a relatively higher volume flows into thecenter pipe 300 at the bottom end 312 of the center pipe 300, since thelarger openings constitute the path of least resistance. Accordingly,for the same reasons set forth above with respect to the scallops 200,uneven G-V-L flow through the catalyst can be minimized to improvereaction efficiency. An enlarged view of the openings 308 taken alongline C of FIG. 3A is illustrated in FIG. 3B.

In an alternative embodiment, as illustrated in FIG. 3C, the openings308 closer to the top end 310 of the center pipe 300′ may be larger thanthe openings 308 closer to the bottom end 312 of the center pipe 300′.For example, the openings 308 toward the top end 310 of the center pipe300′ may have a diameter of about 75 mm, while the openings 308 towardthe bottom end 312 of the center pipe 300′ may have a diameter of about0.1 mm. This embodiment is yet another mechanism by which to adjustG-V-L flow distribution within the reactor vessel 100. An enlarged viewof the openings 308 taken along line D of FIG. 3C is illustrated in FIG.3D.

In yet another embodiment, the openings 308 may increase and thendecrease, or decrease and then increase, along the length of the centerpipe 300, such that there is a non-uniform change in the opening sizefrom the top end 310 to the bottom end 312 of the center pipe 300.

In yet another embodiment, the spacing of the openings 308 on the centerpipe 300 may be modified to adjust the G-V-L flow distribution. In thisembodiment, each of the openings 308 at and adjacent to the top end 310of the center pipe 300 may be spaced closer together relative to theopenings 308 near the bottom end 312, and have a larger opening size, inorder to provide a larger total surface area of openings 308 to increaseG-V-L flow into the center pipe 300. On the other hand, at the bottomend 312 of the center pipe 300, the openings 308 may be spaced fartherapart, together with relatively smaller opening size, so that the totalsurface area of openings 308 is lower at the bottom end 312 than at thetop end 310. Alternatively, each of the openings 308 at and adjacent tothe top end 310 of the center pipe 300 may be spaced farther apartrelative to the openings 308 near the bottom end 312 of the center pipe300, and have a smaller opening size, in order to provide a smallertotal surface area of openings at the top end 310. By way of anon-limiting example, the openings 308 at the top end 310 or the bottomend 312 may be arranged such that each opening 308 is spaced about 0.5mm-25 mm apart from an adjacent opening 308.

As illustrated in FIGS. 3A-D, the openings 308 on the center pipe aregenerally circular in shape, although any shape, such as square,rectangular, triangular, oval, oblong, or any other shape suitable foruse in a particular application, may be used. In a preferred embodiment,the openings are oval shaped.

In one embodiment, the scallop 200 as illustrated in FIG. 2A, may beutilized together with a conventional center pipe having uniform openingsize. In another embodiment, the center pipe 300 and 300′ having thevarying opening size 308, as illustrated in FIGS. 3A and 3C, may beutilized together with a conventional scallop having uniform openingsize. In yet another embodiment, each of the scallop 200 and center pipe300 or 300′ may be used together to optimize G-V-L flow distributionthrough the reactor vessel 100.

In another embodiment, the opening gradient on the center pipe could beconfigured to be opposite of the scallop 200 or outer basket 400, as setforth herein. If the scallop 200 and/or outer basket 400 has itssmallest openings at the top, then the center pipe 300′ would be used,having its largest openings at the top, and vice versa.

As illustrated in FIGS. 3E-G, a profile wire center pipe overlay 318 maybe used together with the center pipe 300, although this is not requiredaccording to the invention. The profile wire center pipe overlay 318functions to prevent the catalyst particles from the adjacent catalystbed 112 from flowing into the center pipe 300. A profile wire centerpipe overlay 318 positioned around the outer surface 304 of the centerpipe 300 is illustrated in FIG. 3G.

As illustrated in FIG. 3F, the profile wire center pipe overlay 318includes a plurality of slots 320 along its length, which may beconfigured vertically or horizontally depending upon the particularapplication. As shown in the enlarged view of FIG. 3F, which is takenalong line E of FIG. 3E, the slots 320 are arranged vertically withrespect to the length of the profile wire center pipe overlay 318. Theseslots 320 allow the G-V-L, which has passed through the catalyst bed112, to flow into the center pipe 300 and out of the reactor vessel 100.

The profile wire center pipe overlay 318 may be formed of the samematerials, and with the same coatings or surface treatments, as profilewire scallop overlay 218.

Modified Outer Basket

One aspect of the invention relates to a “modified” outer basket(hereinafter referred to as a “basket”) for use in radial flow reactorvessels which improves G-V-L flow distribution through the reactor. Thebasket functions the same as the scallops 200 to direct G-V-L flow downthe side of the reactor vessel and then radially across into thecatalyst bed 112. A basket according to various embodiments of theinvention is illustrated in FIGS. 4A-G. The basket utilizes openingshaving a modified size and/or shape along its length in order to adjustthe flow distribution of the G-V-L through the reactor vessel, like themodified scallops 200. The design is to create reasonably equivalentpressure drop across all openings up and down the basket.

Baskets may be constructed of various geometries of an elongated conduitor cylinder. However, baskets may also have different cross sectionalshapes, such as triangular or trapezoidal. They are typically formed ofvarious metal construction which is manufactured into their desiredshape.

As shown in FIG. 4A, the basket 400 is an elongated conduit, such as atube-shaped member, that has an inner surface 402 and an outer surface404. The basket 400 includes a plurality of openings 408 along itslength that extend through the entire thickness of the basket, from theinner surface 402 to the outer surface 404. The openings 408 allow theG-V-L flowing along the exterior of the basket 400 to outflow throughthe basket 400, thus coming into contact with the catalyst bed 112contained in the reactor vessel. The outer basket 400 can be used tomanipulate the distribution of flow of G-V-L through the reactor vesselto optimize the catalyst reaction, similar to the scallops 200.

In the prior art, the openings in the basket are generally of the samesize and shape along the entire length of the basket, typicallyconstructed of profile wire. These baskets have a tendency to cause ahigher volume of G-V-L to outflow through the openings toward the top ofthe basket, since the higher inflow pressure across the same sizeopening causes more G-V-L to flow, while a lesser volume of the G-V-Loutflows through the openings toward the bottom of the basket wherepressure is lower. This creates an uneven G-V-L flow distributionthrough the basket, thereby causing an uneven utilization of thecatalyst. As illustrated in FIG. 4A, however, the openings 408 towardthe top end 410 of the basket 400 have a smaller diameter than theopenings 408 toward the bottom end 412 of the basket 400. By way of anon-limiting example, the openings 408 toward the top end 410 of thebasket 400 may have a diameter of about 1 mm, while the openings 408toward the bottom end 412 of the basket 400 may have a diameter of about75 mm. In this way, when the G-V-L enters the basket 400, a lower volumeoutflows through the smaller openings 408 at the top end 410 of thebasket 400, while a relatively higher volume outflows through the largeropenings 408 at the bottom end 412 of the basket 400, since the largeropenings constitute the path of least resistance. Thus, the basket 400can be used to manipulate the distribution of flow of G-V-L through thereactor vessel to optimize the catalyst reaction. An enlarged view ofthe openings 408 taken along line F of FIG. 4A is illustrated in FIG.4B.

In an alternative embodiment illustrated in FIG. 4C, the openings 408toward the top end 410 of the basket 400′ have a larger diameter thanthe openings 408 toward the bottom end 412 of the basket 400′. By way ofa non-limiting example, the openings 408 toward the top end 410 of thebasket 400′ may have a diameter of about 75 mm, while the openings 408toward the bottom end 412 may have a diameter of about 1 mm. In thisway, when the G-V-L enters the basket 400′, a higher volume outflowsthrough the larger openings 408 at the top end 410, while a relativelysmaller volume outflows through the smaller openings 408 at the bottomend 412, since the larger openings constitute the path of leastresistance. Thus, the basket 400′ can be used to manipulate thedistribution of flow of G-V-L through the reactor vessel to optimize thecatalyst reaction. This embodiment is yet another mechanism by which toadjust G-V-L flow distribution within the reactor vessel 100. Anenlarged view of the openings 408 taken along line G of FIG. 4C isillustrated in FIG. 4D.

In yet another embodiment, the openings 408 may increase and thendecrease, or decrease and then increase, along the length of the outerbasket 400, such that there is a non-uniform change in the opening sizefrom the top end 310 to the bottom end 312 of the center pipe 300.

In another embodiment, the spacing of the openings 408 may be modifiedto adjust the G-V-L flow distribution. For example, each of the openings408 at and adjacent to the top end 410 of the basket 400 may be spacedcloser together relative to the openings 408 near the bottom end 412 ofthe basket 400, and have a relatively larger opening size, in order toprovide a larger total surface area of openings 408 to increase G-V-Loutflow. On the other hand, at the bottom end 412 of the basket 400, theopenings 408 may be spaced farther apart, together with relativelysmaller opening size, so that the total surface area of openings 408 islower at the bottom end 412 than at the top end 410 of the basket 400.By way of a non-limiting example, the openings 408 at the top end 410 orthe bottom end 412 may be arranged such that each opening 408 is spacedabout 0.5 mm to 25 mm apart from an adjacent opening 408. Alternatively,the openings 408 at and adjacent to the top end 410 may be spacedfarther apart relative to the openings near the bottom end 412, and havea relatively smaller opening size, in order to provide a smaller totalsurface area of openings 408 at the top end 410.

The openings 408 on the basket 400 or 400′ are generally circular inshape, although any shape, such as square, rectangular, triangular,oval, oblong, or any other shape suitable for use in a particularapplication, may be used. In a preferred embodiments, the openings 408are circular in shape.

In another embodiment, as illustrated in FIGS. 4E-G, a profile wireouter basket overlay 418 may be used together with the basket 400 or400′, although it is not required according to the invention. Theprofile wire outer basket overlay 418 preferably has the same or similarshape as the basket 400 or 400′ and, in one embodiment, is configured tobe placed into the inner diameter and coupled to the inner surface 402of the basket 400, as illustrated in FIG. 4G. The profile wire outerbasket overlay 418 may be coupled to the basket 400 according to anyknown means, such as, for example, welding. The profile wire overlay 418preferably includes a plurality of slots 420 along its length, which maybe configured vertically or horizontally depending upon the particularapplication. As shown in the enlarged view of FIG. 4F, taken along lineH of FIG. 4E, the slots 420 are arranged vertically with respect to theelongated length of the profile wire outer basket overlay 418. Theprofile wire outer basket overlay 418 prevents catalyst particles fromthe adjacent catalyst bed from flowing into the basket 400, while stillallowing G-V-L to outflow from the basket 400. The size, shape, andplacement of the slots 420 on the profile wire outer basket overlay 418may also be modified, but such modifications will typically not dictateG-V-L flow pattern through the basket 400. However, designs could beused to impact flow through the profile wire outer basket overlay 418.

It should be noted that the basket 400 and the profile wire outer basketoverlay 418 may have any size suitable for use in a particularapplication in a specific type of reactor vessel. In one embodiment, thebasket may be about 1-25 meters long and have an overall bed penetration(smaller I.D.) of about 10 cm-1 m. Their size is not particularlylimited, as it dictates the volume of G-V-L that can be passed throughdepending on the particular application.

The basket 400 and the profile wire outer basket overlay 418 may beformed of any material known to one skilled in the art, including, butnot limited to, metals, ceramics, composites, and the like. In apreferred embodiment, they are formed of metal, preferably a metallicalloy, which is strong enough to withstand the elevated temperatures,pressures and G-V-L flow rates inside the reactor vessel withoutdeforming. For example, they may be formed of stainless steel. Thematerial used to form the basket 400 and/or the profile wire outerbasket overlay 418 is not particularly limited, as long as it hassufficient strength to withstand the operating conditions of thereactor. In one embodiment, although not required, the basket 400 and/orthe profile wire outer basket overlay 418 may be provided with a coatingor surface treatment, such as an anti-corrosion coating.

Although this invention has been described in connection with specificforms and embodiments thereof, it will be appreciated that variousmodifications other than those discussed above may be resorted towithout departing from the spirit or scope. For example, equivalentelements may be substituted for those specifically shown and described,certain features may be used independently of other features, and incertain cases, particular locations of elements may be reversed orinterposed, all without departing from the spirit or scope as defined inthe appended Claims.

What is claimed is:
 1. A scallop for use in a radial flow reactor,comprising: an elongated conduit having a top end and an opposing bottomend and a rounded distribution side; a plurality of openings formed inthe elongated conduit through a thickness thereof, wherein a diameter ofthe plurality of openings progressively increases or decreases from thetop end to the opposing bottom end of the elongated conduit so as toallow a feedstock to flow uniformly out of the scallop through theplurality of openings; and a profile wire scallop overlay positioned onthe rounded distribution side of the elongated conduit to preventcatalyst particles from flowing into the scallop.
 2. The scallop ofclaim 1, wherein the plurality of openings are generally circular,square, rectangular, triangular, oval, or oblong in shape.
 3. Thescallop of claim 1, wherein the elongated conduit is formed of stainlesssteel.
 4. The scallop of claim 1, wherein the elongated conduit has aback side and with the rounded distribution side forms a “D”-shapedcross section.
 5. The scallop of claim 4, wherein the radial flowreactor includes a reactor vessel, and the back side of the elongatedconduit engages an inner wall of the reactor vessel.
 6. The scallop ofclaim 5, wherein the rounded distribution side is exposed to an interiorof the reactor vessel adjacent to a catalyst bed.
 7. The scallop ofclaim 1, wherein the feedstock flows radially through the plurality ofopenings in the elongated conduit of the scallop to come into contactwith a catalyst bed in order to effect a reaction.
 8. A radial flowreactor comprising a scallop according to claim
 1. 9. A radial flowreactor, comprising: a center pipe comprising, an elongated conduithaving a top end and an opposing bottom end; and a plurality of openingsformed in the elongated conduit through a thickness thereof, wherein adiameter of the plurality of openings progressively increases ordecreases from the top end to the opposing bottom end of the elongatedconduit so as to allow a feedstock to flow uniformly into the centerpipe through the plurality of openings; and at least one scallopaccording to claim 1 engaging a wall of the reactor.
 10. The reactor ofclaim 9, wherein the plurality of openings are generally circular,square, rectangular, triangular, oval, or oblong in shape.
 11. Thereactor of claim 9, wherein the elongated conduit is formed of stainlesssteel.
 12. The reactor of claim 9, wherein includes a reactor vessel,and the center pipe is positioned in the center of the reactor vesseladjacent to a catalyst bed.
 13. The reactor of claim 12, wherein thefeedstock flows radially through the catalyst bed in order to effect areaction and into the center pipe through the plurality of openings tobe removed from the reactor vessel.
 14. The reactor of claim 9, furthercomprising a profile wire center pipe overlay positioned around an outersurface of the elongated conduit of the center pipe to prevent catalystparticles from flowing into the center pipe.
 15. An outer basket for usein a radial flow reactor, comprising: an elongated conduit having a topend and an opposing bottom end; a plurality of openings formed in theelongated conduit through a thickness thereof, wherein a diameter of theplurality of openings progressively increases or decreases from the topend to the opposing bottom end of the elongated conduit so as to allow afeedstock to flow uniformly out of the outer basket through theplurality of openings; and a profile wire outer basket overlay coupledto an inner surface of the elongated conduit to prevent catalystparticles from flowing into the outer basket.
 16. The outer basket ofclaim 15, wherein the plurality of openings are generally circular,square, rectangular, triangular, oval, or oblong in shape.
 17. The outerbasket of claim 15, wherein the elongated conduit is formed of stainlesssteel.
 18. The outer basket of claim 15, wherein the radial flow reactorincludes a reactor vessel, and wherein the elongated conduit is arrangedcircumferentially around an inner wall of the reactor vessel, such thatan outer surface of the elongated conduit is positioned directlyadjacent to the inner wall of the reactor vessel.
 19. The outer basketof claim 18, wherein a distribution surface of the elongated conduit isexposed to an interior of the reactor vessel.
 20. The outer basket ofclaim 15, wherein the feedstock flows radially through the plurality ofopenings in the elongated conduit to come into contact with a catalystbed in order to effect a reaction.
 21. A radial flow reactor comprisingan outer basket according to claim 15.